Category Archives: Nerves and Brains

So there is a lot of buzz about the recent discovery of lymphatic vessels that carry fluid away from the brain. There are a couple of reasonable questions: 1) Is this legit? 2) What does this really mean? See below for more details on my parsing of this study.

What did they do?

The scientists investigated how T lymphocytes, a cell with immune functions, could pass through the membranes that cover the brain. Specifically, they used staining techniques to look for where the T lymphocytes were concentrated, since immune cells gather at the gateways into and out of tissues. They then tested the cells next to these areas of concentration to see what kind of tissue the vessels were made of. They used mice and humans. The brains of all mammals share many features, so it is completely reasonable to draw inferences from mouse brains to human brains, but there are some important differences as well, which is why while I enjoy peanut butter, I get bored after running on the wheel for only 3 minutes. The human samples were taken from 9 cadavers.

What did they find?

There is a tough covering over the brain called the dura mater, with channels called dural sinuses between layers of the covering. The team found that the T lymphocytes seemed to be lined up along vessel-like structures. There are blood vessels in the sinuses, and when the researchers used a dye to show where the blood vessels were, they were surprised to find that the lymphocytes were next to an as-of-yet unknown vessel. Additional dye staining confirmed that the new vessels did not belong to the cardiovascular system. The structure of these vessels has some similarities with the rest of the lymphatic system, and some differences. They only found the lymphatic structures in 2 of the 9 humans.

Importance of the study:

We used to think that the brain was largely separated from the rest of the body immunologically. Considering the results of this study, it is possible that certain neurological disorders could be linked to dysfunction of these vessels. Specifically, diseases like multiple sclerosis and Alzheimer’s disease, which seem to be related to changes in immune function, may have mechanisms- and hopefully treatments- different from those we originally thought.

Why we should be cautious:

The fact that only two human brains out of nine showed the structures should make us think twice. Still, there is the possibility that in the cadavers the vessels had collapsed or that t-cell function might not be as robust in dead people. Also, whole brains were used for the mice, and only samples of the dura mater were used for the humans, so those differences might change things too.

Grade on the reporting: C

The image of the location of the proposed vessels in humans that is widely being used is NOT from the study. There is in general too much speculation about what the study found, and not enough focus on the actual findings. There also needs to be more caution about these structures in humans.

A friend of mine recently asked me a fascinating question on Facebook, and I asked if he wouldn’t mind sharing it here, since it touches on the topic of embodiment, and also considers the idea of belief. This question, and my answer, treads at the edge of what we can currently know and may make some science types uncomfortable. I have tried to keep the ‘sciency’ parts on the science side, and be clear where I am crossing the line.

Markus asks:‘Does faith reside in the brain or the heart? As a neuroscientist, do you believe the brain to be a transducer or a generator? Perhaps both? As a man of faith, where does one determine mind to begin? These questions are sincere as I have experienced through meditation that I am not what I think, that I cannot determine where some perceptions originate and that sometimes I can perceive the thoughts or emotions of others without being physically near them. It leads me to suspect that consciousness, awareness reside beyond the cerebral organ itself. Spiritually, I feel connected to and informed by a source greater than the grey matter I am currently renting. Your thoughts?’

Tell me where is fancy bred.Or in the heart or in the head?How begot, how nourishèd?

It is engendered in the eyes,With gazing fed, and fancy diesIn the cradle where it lies.Let us all ring fancy’s knellI’ll begin it.—Ding, dong, bell.Merchant of Venice, Act 3, Scene 2

That was a little Shakespeare to address the same question but with respect to love. The singer in the Merchant of Venice concludes it is born in the eyes. While I can entertain the notions of faith and love from a poetic standpoint, and conceive various bodily origins as an artist, as a neuroscientist I can say that they are both born in the brain. However, I would be very quick to add they are born in processes that we normally ascribe to the heart. So I would say faith is born in the ‘heart’ of the brain: it is an affective process that emerges after we have, in the words of Bruxey Cavey, ‘run the ramp of reason’.

The brain is certainly both transducer and generator. If we begin with a simple percept, like sound, the sensory apparatus of the body is stimulated by fluctuations of energy in a particular frequency range. Those vibrations are passed by neurons to specialized portions of the brain that decode and categorize the information. Interestingly, the ear itself makes sound like a noise cancelling headphone (evoked otoacoustic emissions), so that anticipated frequencies are enhanced, and unanticipated frequencies are filtered. Those emissions are generated by the brain, so that the ear is not just a passive device. In this way, the brain is clearly also a generator. Ultimately, the brain takes the percept of sound, and the person hearing chooses a response, based on current and remembered conditions: is the sound alarming or pleasant? rhythmic, melodic or both? does it have meaning to us? do we have a previous association with it? All of these things factor into our response to the sound, which requires our ongoing participation in an environmental context, or ground, through the activity of our bodies.

The ‘beginning’ of the mind of the mind is an interesting concept. It presupposes that the body ends somewhere, and that the mind is ‘located’ in a different place. (Here, I take my lead in my thinking from Antonio Damasio, Kevin O’Regan and Mark Johnson, who are eminent neuroscientist, perceptual scientist and philosopher, respectively, but there are numerous other authors on the topic of embodied cognition.) A brain is a collection of specialized cells called neurons that can only function in a living body in an environment. Brain cells are like any other cell: they require homeostasis, that is they need the Goldilocks conditions of neither too hot, nor too cold, nor too acid, nor to alkaline… it needs to be ‘just right’. Brain cells metabolize, they use proteins to record and pass along information. They can also simulate previous experiences, allowing us to predict, remember, dream, create and imagine. A ‘thought’ is not a place in a brain, or out of it, or a thing we can touch. It is the organized activity of millions of neurons over time. Likewise, a ‘mind’ is not a thing. It is a process of millions of thoughts, both remembered and in real time. Trying to point to a ‘mind’ is like trying to point to cellular metabolism: you can witness its effect, and you can see that it is present, but you can’t touch it. To use a metaphor, we can see the evidence, effect and impact of love, but love is a process rather than a thing. As a completely different metaphor, you can see the evidence of the process of baking on a muffin, but you can’t touch baking. To quote Damasio, ‘body and mind are different aspects of specific biological processes’.

Overall, I reject the thinking of both Descartes and Plato, and do not believe that mind is distinct or separate from the body. I do not see the support for such an idea philosophically, theologically, phenomenologically or physiologically. I also think that such a division is incredibly problematic. The famous educator and philosopher John Dewey notes, ‘The very problem of mind and body suggests division; I do not know of anything so disastrously affected by the habit of division as this particular theme. In its discussion are reflected the splitting off from each other of religion, morals and science; the divorce of philosophy from science and of both from the arts of conduct. The evils which we suffer in education, in religion, in the materialism of business and the aloofness of ‘intellectuals’ from life, in the whole separation of knowledge and practice — all testify to the necessity of seeing mind-body as an integral whole.’ Of course, I do not think an integrated mind-body is simply a matter of a point of view, I think it is a tacit physical fact.

Your comment about sensing the thoughts or emotions of others from afar is interesting. I can offer no plausible scientific explanation, although that doesn’t mean there isn’t one. The closest I can come is this: We can measure the organized electrical activity of the brain. We do this using an electroencephalogram (EEG). In some instances, we can discern whether the person observed is in a restful state, if they are learning, if they are an expert, if they are tired or agitated, or any number of things. We can also influence the electrical activity of the brain using a technique called transcranial magnetic stimulation (TMS). We can stop a person’s hand from moving, or cause them to not be able to hear things, or temporarily forget, or to learn more quickly. In short, our brains give off electrical signals and are influenced and changed by electrical signals (which is why I will never wear a Bluetooth headset). What has never been scientifically proven, but is conceivable in my view, is that the electrical activity of one brain may be able to influence the electrical activity of another brain. What is the effective distance? I have no idea. But groups and cultures carry ideas and thinking as surely as do electromagnetic waves, so who knows how sentiments and ideas may travel? This is purely speculative, and I have no proof at all, and no real idea.

You spoke of your connection and information by a source greater than yourself. In this respect, we are certainly thinkers within a cultural and social context, and without question, the thinking and behaviour of others will influence our own thinking and behaviour. There is considerable evidence to suggest that the grey matter you ‘rent’ is also inhabited by the thoughts, opinions, attitudes and ideas of others, both remembered and in real time. And now I will completely step away from my role as a scientist, and talk about things that cannot currently be proven using direct observational methods. There is always the possibility that there may be things outside of us that are bigger than we are and which change and influence us: things that some people call God or cosmic energy or long-distance soul calls from loved ones. How do we know to call someone on the other side of the world at the exact moment they were thinking of us? Those things may have mundane everyday explanations that we have not yet understood or been able to quantify. Those things may have mystical explanations which may elude scientific investigation for a very long time. One the other hand, there may be a very clear scientific explanation that intersects with mystery in the same way that Brownian motion in boiling water intersects with the mystery of the glory of tea. I like the words of the thoughtful Christian theologian N.T. Wright in his very thoughtful post on mind/body dualism, ‘God is always at work in the world, and God is always at work in, and addressing, human beings, not only through one faculty such as the soul or spirit but through every fibre of our beings, not least our bodies. That is why I am not afraid that one day the neuroscientists might come up with a complete account of exactly which neurons fire under which circumstances, including that might indicate the person as responding to God and his love in worship, prayer and adoration.’

This post is in response to a question from Rich:

What are your thoughts on the effects of cellphones on our bodies? I’ve been having issues with my right hip flexor for a year. It obviously gets better when I do my stretching and exercises, but I wondered if the fact that I keep my iPhone in my right front pocket might play a role, since the discomfort emanates from the same place that my phone sits in my pocket. Have you read anything that has influenced where you keep your phone?
(I’m not talking about the structure of the phone causing discomfort. I’m wondering about the electronics within the phone…). The pain is a tension that runs up my IT band and then makes a right angle turn across the front of my quad at the place where my pants crease when I sit. Then occasional dull aching in that area. If I had my phone in my pocket, it would press on that area when I sit. (I take my phone out before I sit, btw.)

Hi Rich:

Thanks for writing. I will confess right away that I had to do more than my regular amount of sleuthing to get at this question which is interesting for a couple of reasons: one of them being that almost immediately after I received your question, a massage client asked a question about a nearly identical pain, but did not mention where he carried his phone, although he had a very tight iliacus and psoas muscles. I will come back to that in a bit. Another thing that is interesting about your question is the nature of pain. Pain has many possible inter-related causes, and is a complex affair, related to some kind of stimulus that is damaging or has the potential to damage tissues, but also related to perception, mood and many other factors which I will not really deal with in this post. Additionally, pain in one part of the body might be caused by a problem in another part of the body altogether, and this is known as referred pain. Your question asks in essence, might it be the electronics of the phone causing the pain and not the phone’s physical size and presence? I think this is a pretty reasonable question. In all instances, I should say before I get down to brass tacks, if pain is persistent, consult your medical professionals.

The easiest way to find out the answer to your question would be to take a 1200 people, stick working cell phones in the pockets of 400, just the active electronic bits in the pockets of 400, and disabled cellphones in the pockets of the remaining 400. Then have half of each of those groups put the stuff in their left pocket, and half put the stuff in their right pockets and find out who complains after a year and what side. It might be tough to get ethics approval because we aren’t really allowed to intentionally put people at risk. No one has yet done this study, so we will have to go with the existing research to see if we can figure out an answer.

The pain you describe corresponds with the location and sensations related to the lateral femoral cutaneous nerve (LFCN). The LFCN emerges from your spinal column around the level of the second and third lumbar vertebrae, dives between the quadratus lumborum and the psoas muscle, goes behind your guts, down across the front of the iliacus muscle (which lines the inside of your iliac bone), but underneath the sheath of fascia that covers that muscle. It then goes underneath the anterior superior iliac spine to emerge from under your inguinal ligament, over top of, or sometimes even through your sartorius muscle, and then under the fascia latae of the thigh. The take home message, is that the LFCN does a lot of weaving under and over stuff. The image below from Gray’s Anatomy shows where the LFCN emerges from under the inguinal ligament, which I will talk about more below. When your cell phone is in your front pocket, it is probably pretty close to the LFCN.

Looking up the right side of the pelvis from underneath. The lateral cutaneous femoral nerve is the small yellow structure on the left, just above the iliacus muscle. The big round structure is the socket of the hip joint (Gray’s Anatomy).

Part of the problem of answering your question is that cell phones are really too new and too rapidly changing in terms of size, shape and internal components to get a consistent read on what problems they might cause from either a mechanical or electronic standpoint. Cell phones only became pocket-sized in the mid-90s, and since 2002, smart-phone use has climbed from just over 50% to 90% of American adults owning one (http://www.pewinternet.org/data-trend/mobile/device-ownership/). This all means we don’t have a long list of case-studies to draw information from. What we do know radiation-wise is that while a cell phone is in your pocket in the on position, it will ‘ping’ nearby towers intermittently to let the network know where it is so that it can receive incoming calls. This will generate tiny amounts of radiation in the radio frequency. Talking on the phone itself generates a greater amount of radio frequency radiation as would happen if you used either a wired or bluetooth headset with the phone in your pocket. What we need to know about for your question is if the cell phone’s radio frequency could produce damage to nerves that could induce the perception of pain.

Radio frequency radiation might potentially cause damage to nerve cells due to heat, or by the disruptive effects of the radiation itself. Because we typically use cell phones next to the brain, which is a big, sensitive group of neurons, most studies with cell phone radiation focus on that structure. Quite a number of experiments have been done with cell phone frequency radiation and rodents. The results are variable, with some studies showing damage to the DNA of nervous tissue (Diem, Schwartz, Adlkofer, Jahn & Rudiger, 2005), and other studies saying there is no damage (Utteridge, Gebski, Finnie, Vernon-Roberts, & Kuchel, 2002). (Of course the real problem with cell phone use in mice is the roaming fees.) In humans some studies show a link with increased brain cancer risk in long-term cell phone use (Khurana, Teo, Kundi, Hardell & Carlberg, 2009), but other studies do not show this link (Lajavaara, Schuz & Swerdlow, 2011). There have only been a few studies on cell phone radiation and thinking, but nothing conclusive. More to the point, there is no direct evidence at this moment that placing a phone next to your brain changes the way you perceive pain, and besides, your question is about putting the phone in your pocket.

Radiation can certainly cause damage to peripheral nerves (nerves outside the brain and spinal cord) resulting in pain. Such damage is found at times in cancer patients who receive radiotherapy to treat the cancer (Stoll & Andrews, 1966). However the type of radiation for cancer treatment is typically x-rays, gamma rays or some form of particle radiation, which is at a much, much higher energy than radio frequency, and the focus is remarkably tight and concentrated. In comparison, placing a phone in your pocket would produce very small amounts of radiation, would be diffuse, and would differ from day to day because of differences in the placement of your phone and your clothing.

So in the end it is possible that a cell phone’s radiation could cause the pain you describe, but I think it is unlikely. Which brings me back to my client. After I got your question, I called him to ask about where he carries his cell phone – same or opposite side of the pain. Turns out, he doesn’t carry it in his pocket at all. Which made me wonder if something else was going on.

There is literature about a condition causing a very similar pain to yours (and the pain of my client). It is called meralgia paresthetica, which pretty much means ‘thigh pain felt in a weird place’. Meralgia paresthetica is a painful, burning, muscle aching or sometimes even numb feeling on the outside of the thigh, or along its crease, caused by a compression or entrapment of the LFCN. As mentioned before, the LFCN emerges from under the inguinal ligament which runs from the Anterior Superior Iliac Spine of each side of your pelvis, down to the pubic bone. Its big job is to keep your nerves and muscles and other leg bits from blobbing out all over the place. The inguinal ligament is what causes the appearance of the ‘fold’ at the top of your thigh (exactly where your pants crease), showing the division between your torso and your leg. Sometimes through sudden weight gain, or swelling to the tissue behind the inguinal ligament things get pressed up against it, causing a pinching or discomfort. My client, for example, had very well-developed hip flexors, particularly the iliacus and psoas muscles which were also very tight. In fact, in some people you can induce a ‘pinching’ sensation at the inguinal ligament by bringing the hip into extreme flexion, since the tissues behind are being pulled up against the ligament. In my clients with such pinching (and in myself as well), I can alleviate the pinching in extreme flexion by thoroughly stretching the hip flexors.

While the LFCN could be compressed anywhere along its length, the most common location of entrapment is where it exits the pelvis (Grossman, Ducey, Nadler & Levy, 2001). The inguinal ligament is so prominent in anatomical causes for the condition that some surgeons have developed a method of relieving meralgia paresthetica by surgically loosening the ligament (Alderich & van den Heever, 1989). And that brings us back to the phone in your pocket, which led me to think of the article ‘Meralgia Paresthetica from a Wallet’ (Orton, 1984) in the Journal of the American Medical Association. In the abstract Orton says ‘I noticed an aching, burning sensation along the left anterolateral thigh on the side of the wallet. It also was worse while driving any distance.’ The condition has also been induced by tight pants (Boyce, 1984). Depending on the way the nerve is situated, it is conceivable that the condition could be induced by any pressure along the inguinal ligament, either from pressure directed inward from the outside by clothing, wallets or phones, or from pressure directed outward from the inside, by weight gain, pregnancy or big, tight, developed iliacus muscles.

There are completely different possible causes for your pain that have nothing at all to do with rectangles or electronics in your pockets (What has it got in its pocketses?) or even with meralgia paresthetica, so I am not saying you have cellphone-induced meralgia paresthetica (because I am not the right kind of doctor to make a diagnosis), but from all evidence it seems much more likely than a nerve problem caused by radiation. And this might be true even though you remove the phone when you sit, since any irritation at all to the LFCN could be sufficient to cause the pain.

The best thing to do in either case is to take your phone out of your front pocket, which will prolong the life of your phone and get its electronic and mechanical influence, if any away from your body. Time will tell what kind of effects these devices have, and it won’t hurt to show a little caution. Also continue to stretch your hip flexors using postures like the yoga low lunge. Even if the cause is completely different, we spend so much time sitting that such a stretch will have benefits that are well worth your time, especially after a long drive.